LONDON — After years as the poster boy of the Paralympics, a chastened Oscar Pistorius moved Monday to defuse the row that threatens to blemish the clean-cut image he forged during a protracted struggle for acceptance within sport.

Throughout numerous legal fights to be allowed to compete alongside able-bodied rivals, Pistorius could at least always count on returning as the icon of the Paralympics and collecting gold medals.

But the era of Paralympic invincibility for the so-called “Blade Runner” appeared to end when his bid for a third straight gold in the 200 meters was thwarted Sunday night by another double amputee on carbon fiber prosthesis.

Victory seemed certain for Pistorius when he reached the bend on the London track, but Alan Oliveira of Brazil came storming down the home straight on his blades to overtake the defending champion.

Rather than hailing his rival, Pistorius accused the 20-year-old Brazilian of gaining an unfair edge by using lengthened blades. That’s despite spending years himself convincing authorities that he should be allowed to compete in the Olympics — a feat he achieved last month — because his prosthesis did not influence his athletic capabilities.

Having called on the world to focus on the abilities of athletes rather than their disabilities before the London Games, Pistorius has shifted the spotlight back onto the advantage technology might provide.

To many, the South African sounded like a sore loser by launching his tirade within minutes of his first ever Paralympic loss in the 200, failing to defend the first of three titles from Beijing.

“I would never want to detract from another athlete’s moment of triumph,” he said in a statement on Monday. “And I want to apologize for the timing of my comments.”

However, Pistorius was unwavering in his determination to ensure the International Paralympic Committee tightens the formula used to calculate the acceptable length of blades.

“I do believe that there is an issue here and I welcome the opportunity to discuss it with the IPC, but I accept that raising these concerns immediately as I stepped off the track was wrong,” Pistorius said. “That was Alan’s moment and I would like to put on record the respect I have for him.

“I am a proud Paralympian and believe in the fairness of sport. I am happy to work with the IPC, who obviously share these aims”.

The IPC insists the length of Oliveira’s blades were proportional to his body, with all the finalists measured before Sunday’s race. But the IPC knows it cannot ignore perhaps the only globally recognizable star of the Paralympics.

“Clearly we don’t want athletes running on stilts,” IPC communications director Craig Spence said. “What we need to do is have a formal meeting with all the experts in the room. He might propose some changes, but out of credit to the athlete, who has done so much for the Paralympic movement, those comments he has shouldn’t fall on deaf ears.”

The formula that determines the length of blades allowed calculates the predicted height of an athlete, plus 3.5 percent to account for the on-toes running position.

Pistorius’ maximum allowable height is 1.93 meters, yet he opts to stand at 1.84m in blades that were subjected to stringent testing in 2008 to show they provide no advantage when competing alongside able-bodied rivals.

Oliveira, whose limit is 1.85 meters, claimed Monday that his blades gave him a race height of 1.81 the previous night.

“The coaches and I decided to try a higher blade,” Oliveira was quoted as saying by The Guardian. “I tried the new height for the first time last year and it was difficult to get used to them. I decided to try them again earlier this year and it went a little bit better. Three weeks ago, we decided to really go for it.

“The prosthesis don’t run alone. Of course they are good for an improvement, but there is not a significant time difference.”

While Pistorius claimed it was an unfair race because he couldn’t compete with Oliveira’s stride length, South African sports scientist Ross Tucker found that the loser in fact took six fewer steps than the winner.

“The leg-length issue is an ‘advantage’ that Pistorius has always had, and we’ve been watching him compete for years not knowing if he’s done the exact same thing as he is now accusing Oliveira of,” Tucker wrote in an analysis of the race on his SportsScientists.com website.

The row threatens to rumble on for the remainder of the Paralympics, with Oliveira potentially standing in the way of Pistorius repeating his trio of golds in Beijing.

Next up is the 4×100 relay on Wednesday, before Pistorius bids to defend his titles in the 100 on Thursday and 400 on Saturday if he reaches the finals.